Machinedesign 1851 Scratch Match 903 0 0

Fun With Fundamentals: Problem 272

Sept. 1, 2003
This one will have you on spins and needles.

Problem 272// Scratch match

Bobby Ray thinks he’s got the right moves to mix and scratch with the best of them. Practicing for weeks, the Ray-man is planning to enter the Greater Northcoast Regional Turntablist Competition to prove his grooves have what it takes to make the people get freaky on the dance floor. His friend Jimmy, concerned that Bobby Ray will be devastated once he finds out he’s the unfunkiest disc jockey around, has gone over to Bobby’s house every day to try to dissuade him from entering the competition. With the contest just a few days away, rejection looms close on the horizon.

Bobby Ray feels he tears it up and breaks it down with the most righteous songs this side of town. If he’s planning on busting his groove with a 12-in.- diameter record, what are the magnitudes of normal and tangential acceleration at the record’s edge after he has scratched his record with an angular acceleration of 10 rad/sec2 for two turns? Assume his old 45 is scratched in the original direction of spin.

Solution to problem 271, Sound training, August 2003:

Winners circle

Fun problem 270: Faucet finish July 2003
Total entries:
37 Number correct: 16 (43%)
Jeremy Elder
Jeremy’s prize:
MechPack 2000 software from UNIK Associates, Milwaukee.

Reduce hours spent calculating to minutes. MechPack 2000 helps determine the capacity of flat belts, size pulleys, convert belt speed to rpm, and quickly calculate many other use factors. Most programs use English and metric units. Online help and phone support are available.

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Fun With Fundamentals: Problem 271

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